His younger brother Robert Sheehan is an international heartthrob, and the apple doesn't fall far from the tree for competitive fitness physique athlete Brendan Sheehan.
Raised in Portlaoise, the 6ft 4in commercial model was always encouraged to play sports by his parents, Maria and Joe Sheehan.
"My dad is from Kerry, so 90pc of what comes out of his mouth relates to Kerry football. He always had old videos of football matches on and was a big boxing fan, so I guess that is what ignited the initial spark."
"I probably tried just about every sport there is or I had access to. During the Stephen Roche and Sean Kelly era, I fancied myself as a future Tour de France winner. Then in the 1990s, as the World Cup success gripped the nation, I was a future Packie Bonner. As I entered my early teens, I moved on to athletics, competing for Co Laois."
However, it was only in his late teens that an interest in building muscle and being able to defend himself arose, inspired by former professional bodybuilder Arnold Schwarzenegger, who gained worldwide fame as a Hollywood action film icon.
"I used to watch him pumping iron over and over again and gather whatever heavy equipment I could from the backyard and attempt to do exercises I had seen him do."
"After meeting some fellow eager gym-goers, my love for working out in the gym and trying to build my body took over and became a passion of mine."
The 30-year-old fitness fanatic first started to participate in national and world fitness competitions in 2012 and has won the fitness section of the national bodybuilding championships twice.
"I compete as a fitness physique athlete. It's a natural Men's Health kind of look. I wouldn't classify it as bodybuilding. It's an obtainable lean physique more so than muscular."
His first competition in the World Fitness Federation's Mr Universe saw him come seventh.
"I got this opportunity through meeting personal trainer Paul Byrne. I told him I would love to compete, but being 6ft 4in and naturally very skinny, I could never compete with the big guys.
"He said he was trying to develop the fitness physique category and was putting together a team for Ireland. My physique was right, so he put me forward.
"This was something from a very young age I had dreamt about doing as I had idolised the champions."
Fitness physique athletes have toned muscles with very little body fat, but the challenge to transform one's body can be immense.
"You are drained mentally and physically. The workouts are gruelling, eating is so precise, all food is weighed, all accounted for and only what the plan allows goes past the lips.
"The social life becomes non-existent. Going out can just be frustrating as people try to force alcohol into you, but it's all worthwhile when the day comes and you stand on stage and know you are strong enough for all those challenges, temptations and not only that but you're good enough to win. The adrenalin rush is better than any rollercoaster."
2012 was the first time there was a fitness physique category in the NABBA bodybuilding show, the first and original competitive bodybuilding association.
"I won that and I also won the spring classic, which was in April of this year. It feels incredible. I am so proud of my achievements so far as it has created a lot of opportunity for me in the industry.
"From getting to know Paul, he offered me a job as a personal trainer in his well-known and well-respected gym BodyByrne. I was just qualified, so to get such an opportunity was great and I snapped it up."
A sponsored Optimum Nutrition athlete, one of the world's biggest sports supplement brands, Brendan will enter his next fitness physique competition in April when he is in tip-top shape.
"I will probably enter a few shows around that time. There are different federations and there are fitness modelling shows now too which again would suit my physique more."
The regime from now until then consists of training, eating and sleeping – three key and integral components to his success.
"The body has to be symmetrical, defined and somewhat muscular, so each body is different and different body parts respond in different ways. I train each body part differently, depending on what needs to happen to that muscle to create a better overall physique.
"My legs are out of balance with my upper body; they need to grow before my upper body does, so really emphasising them. Yesterday, I trained them with incredible intensity."
At the moment, Brendan is training up to six days a week lifting weights, but as the competition gets closer, he will introduce more cardio training to reduce his body fat.
All food is weighed and written down to such preciseness that included are the amount of grams of protein, carbohydrates and fats he eats on a daily basis – all in aid of having that leaner physique with taut limbs.
"I have goals around this, so being precise like this helps me stay motivated. My eating isn't restricted all that much. I eat fresh food, pretty much nothing that has been processed. I do like eating out and enjoy my wine at dinner and some drinks at weekends. However, about 12 weeks from a show, I will cut out alcohol."
The closer it gets to competition, the more difficult it can become. "You are cold because body fat is low, tired because of calorie deficit and intense training which can lead to crankiness too. An understanding partner is a must but luckily my girlfriend also competed in the bikini section last year, placing second and fourth."
Alcohol is first to go and dining out in restaurants can become tricky.
"Eating out becomes difficult because of the amount of butter used and deep-fat frying foods. I have often gone to dinner with my lunch box with my prepared food and ate it under the table."
For those who feel he is pushing his body beyond normal limits to achieve perfection, he says: "Health is what's most important to me. I don't do severe dehydration, starvation or anything along those lines. In my last four weeks before a show, I still eat seven meals a day – 3,000 calories in total (1,000 from carbohydrates) – and drink plenty of water. It's about understanding your body, input versus output and manipulating food to look a certain way on the day.
"I weigh all my food, lunchbox it up and bring with me if I am out and about. Every three hours, I stop and eat, no matter what."
While his brother Robert has been busy with television roles to date, such as Nathan Young in Misfits and Darren in Love/Hate, he still supports Brendan in all he does.
"Robbie and I are more than brothers, we are best mates. I love and adore that inspirational young man and he loves what I do too. He is away a lot now and I really miss him. He really does inspire me and we encourage each other to shoot for the stars and be the best we can be."
Brendan Sheehan is represented by Fraser Models and Actors www.frasermodelsandactors.ie www.facebook.com/BrendanSheehanFitness