@Grams --typically this happens when you add parents to a child, then next time, when you are adding the same parents to his siblings, you use the just add father/mother on the page instead of adding the child to the parents page ( RM should say do you want to add this child to this family ? BUT it doesn’t)-- if this is the problem, as MYoung said 1st check to see if part of the children are under one couple and the rest under the other couple and if there is more than 1 marriage fact-- if so then unlink the kids from one couple and link them all to the other-- just make sure you check that the info under the marriage fact is the same as sometimes one has more info–after that unlink the wife from the hubby ( same is probably true for 2 marriage facts–a child is listed under both)—from what I can see, it looks like the son James is listed twice under each couple…
BUT I will also mention this thread from a few days ago
Basically Patrick said a while back he imported a gedcom into his database then merged duplicates causing the person to show up on a marriage list twice BUT there is only 1 couple and 1 marriage ( not sure I agree as to how it happened)–if this is the problem, you have to UNLINK EVERYBODY and then link them all back together to get the phantom marriage and couple to disappear… ,