Can you tell me is benching 105 healthy for a 13.6 year old?

Depends: This depends on how far into puberty the child is and, yes, whether this is a boy or girl. To bench that weight the child should be a boy who is at least a year or two into puberty where he has the increased bone strength to handle this amount of weight. 13 1/2 year old boys vary greatly - talk to kids pediatrician whether they are ready or not yet.

Adolescent: At your age you should be under the watchful eye of a coach. Bench pressing that much weight may be too much for your body.