15 year son, can see and feelepigastric pulse, he is thin BMI 20.2, bf 17%. No pain in epigastric area. He always exercise's. Need to worry?

Get Checked. This is often normal, , but only someone who knows what the abdomen should feel and sound like and who actually checks your son can know for sure in his particular case.
Probably not. If he is an otherwise healthy teen, the pulsation is likely coming from his aorta, the large blood vessel that takes blood from the heart to the abdomen, pelvis, and legs. The aorta is often palpable in thin patients. P.S. You're 23 y/o and have a 15 y/o son?