How old is to old for a son to sleep with his dad?

In my opinion, kids should never sleep with their parents. Having said that, I'd put an upper limit at about 3. Note that this is my opinion only.

Please tell us more,

Do you mean for a short time while they are scared in a storm.

Do you mean perhaps on a overnight trip or visit.

Please give us the details about this

Id say about 5-6 years old. After that he should learn to be in his own bed.

I would say that's pushing it a bit, we had up until 3, was quite often, but its just every so often, usually if one of us is not coming home for the night because of work, to not feel lonely in the bed...

Id say 5. my daughter coslept with us until the day she turned 5.

This is a huge opinion based question. Many familys co-sleep.

However, it really is pushing it once you get past 5 or 6.

I agree with 5 or 6 especially as an every night thing.
I would still get up and get into my parents bed until I was around 9 or 10 but it was rare.