It is possible at age seven, that this little boy has realised that he has no mum in his life, whereas most other children do have a mum in their life. It is certainly not uncommon for a mum to be missing for a variety of reasons, but it’s possible he’s realised and wonders why. My son and his partner adopted a little two year old boy, who is now eleven. He was always told he is adopted. They explained the lack of a mum in his life by telling him that he does have a mum, but she wasn’t able to look after him when he was a baby, and so he went to a foster family at first, but then they adopted him, and he is now their son forever. They try to ensure that he has female role models in his life, that’s partly where I come in, but I’m his nana anyway. Then there’s his other grandma and four aunties. He has two female cousins as well as two male cousins. On Mother’s Day my son always makes sure he has a card for me, so he can take part in the social ritual of celebrating Mother’s Day, and he always gives me the gift rather than my son giving it to me.
I may be barking completely up the wrong tree here, but that’s what I wondered when I read the OP.
The rest of it all seems like a very normal life for a seven year old.