Absent father

As he doesn't live with his son and hadn't been good at communicating, then the person who does the looking after gets the say, in my opinion.

How old is your grandson now? He has two half-siblings from his mother's new relationship so a few years must have passed.
You say communication from your son has been intermittent, maybe the birth of his new baby has made him think about his son and want to rebuild this relationship.
I think your grandson should know about his half-sister.

If the son was 6 when your son left what is he now? 10? Older? I think your grandson should know about his half sister. While he doesn't know he might be spared some feelings but I think it's far worse for him to find out later with the added slap that he wasn't told. This is especially true if he accidentally finds out. Not knowing may be damaging in the long run.

I think he should know but your son needs to understand what he has done to that child. This could potentially ruin his confidence. He wasn’t good enough for his Dad so he’s gone and made more kids.
When is he going to visit?
Maybe the news would be better in a 1-1 visit where he can give him undivided attention.
Why should mum deal with all the trauma and fall out?

It doesn’t really matter what strangers think. The decision is his mother’s.

If the mother is caring for his child the very least the father should do is respect her wishes. She knows the boy best and perhaps as time goes on she may decide he would be best knowing, but it is her decision.

trisher

If the mother is caring for his child the very least the father should do is respect her wishes. She knows the boy best and perhaps as time goes on she may decide he would be best knowing, but it is her decision.

Yes. Mum knows him best.

Again it’s only the mother that can make this decision as she’s his carer It sounds as if your son opted out when his son was 6 and left the child’s mum to deal with all the fall back which his absence caused
Does you son support his child financially, and is the grandson happy with his two half siblings at home ?
Whilst I agree he should know about his new half sibling it needs to be the mums decision when and maybe waiting till he’s older is better If he’s 10/12 now he will be going through his own life changes

IMO he should be told. He may not thank his mum in the future if he finds out this was kept from him.

I agree it is up to the mother to decide.

Bibbity, you have a great point - 100% agree!

My cousin, who has had an interesting personal life, had twins with a short lived partner. He only told the children from his first marriage when the twins were three!

Good point Bibbity I think it's down to the child's mother to decide when and how this information is passed on. I do think the child should be told at some point.

It is easier to be open and honest with the child. He will be much more upset if he finds out in the future IMO.

Perhaps the boy has had problems adjusting to his two younger siblings and his mum knows this.She may just be giving him time to adjust, so she might tell him later. Either way it's her decision.