I have one DC from a previous relationship and two with my husband. All three have been treated as OUR children by the majority of the family.
However, one couple on H's side wouldn't ever buy birthday or Christmas gifts for our eldest. When they had DC of their own (3 years ago) they started buying for him.
However, h and I separated 4 months ago but still on good terms. This Christmas all his family bought for our three children with the exception of this couple. They did buy for my H's biological DC though.
AIBU to think this is disgusting? Just because we are no longer together doesn't mean my eldest is not H's child. To put into context, H has been in eldest's life since age two and he does not see his biological father and receives no gifts or maintenance from him. My H still considers him as his son and pays maintenance for him.