8-) That would just make the marriage doubly anullable. Usually one party is bringing the annulment. I've never heard of two people petitioning at the same time.
But those of the same mind are not in disagreement. Annulment grounds only speaks to those seeking out, not to whether it is intrinsically wrong for couples to happily not desire children. I think there are other rules that apply to Catholics on that, but I am far from the one to find it and quote it, I am not Catholic :~D