The only thing that I think matters from the article is this:

This building of extended family by choice shouldn’t be diminished, said Qian of UBC, noting that “voluntary kin” is common in many 2SLGBTQ+ communities, and we don’t have to define family based on blood ties.

If you think that having cousins should be a vital part of your child’s life, just have friends that have children around the same age as your children.