You are right and some of them were also killed out of their rightful time because of birth control pills which cause many otherwise viable embryos to not be able to connect to the uterine wall and they therefore they are killed. Many parents will be shocked and grieved to meet their sons and daughters in heaven that died at their hands.
Why would they be grieved? They gave their kid a first-class ticket to heaven--being united with the Lord without delay!
Seems like the best gift a parent could give a child, if what some say is true! While that doesn't make it less of a sin of the parents, it's a great deal from the kids' point of view. After all, if they truly want to know the experiences of temporal life on this earth, and they truly are in heaven, they should be able to do so at their whim.