About ILs ISA contribution?

[Mvmmy]

DD1 was born 2015 and my parents and ILs very kindly offered to contribute an amount to her ISA.
DD2 was born in 2018 and my parents kindly contributed same amount as DD1 had but ILs have contributed half of what they gave DD1 and haven’t said why.
DH doesn’t think it matters - AIBU to think this is unfair on DD2?

Their finances may have changed.

Maybe they can't afford as much. I'd make up the difference, if it were me.

Maybe they can’t afford it, maybe they can’t remember.
My two will end up with different amounts in their savings accounts for numerous reasons.
My plan is to simply redistribute so they have the same or make up the lesser one when the time comes.
I’m not sure, but believe they can’t withdraw the money until they are 16 anyway so it shouldn’t be an issue for a good while.

They probably can't afford the same.

My parents gifted a substantial sum to my sibling for a house deposit. This year they've gifted my OH and I a still substantial sum towards our deposit but I'm aware it's less than half of what my sibling received.

To be honest, I'm just grateful for the help and grateful I've had this opportunity to get on the property ladder.

I wouldn't worry about it, it really probably is just a change in finances. My parents had the original sum at that time, and this year they were only able to help me because a relative bequeathed them something.

You could drop a little extra into the ISA over time to even it out (unless we're talking a difference in the thousands or millions).