I would prefer to have separate portfolios. The wife is free to accumulate more, as well as the husband is free to go an extra mile to make his portfolio become huge and massive. That way, regardless if they stick together or file a divorce in the future, bitcoins are safe within their separate wallets.
However, if they wish to have another joint portfolio for their future children, I think that would be great. Seize while the iron is hot, as we cannot predict what will be the future for bitcoin.
But did you know that the way to maintain a strong and lasting marriage over time is to trust each other, and to do that, we need to share everything with each other. If each person has their own investment, it will unintentionally create mutual suspicion, causing cracks in the relationship between husband and wife and family. Family may no longer be happy but instead there will be calculation and jealousy of each other. Any relationship cannot last if money is put first in that relationship.
Furthermore, if both husband and wife think about the future of their children, they will never suggest or agree that each should have separate property. Only selfish parents who do not care about their children's future think about owning their own property.
I don't know if you are married, but I bet a child will never have complete happiness and comprehensive development without the love of one of the two. Therefore, before getting married and having children, couples should stop being selfish and think more openly.
Bitcoin is just money, and lost money can be earned back, but the future of our children, once lost can never be saved.