When one of the partners is significantly older, the benefit of hindsight and wisdom can smoothen a lot of rough patches that couples will go through in their marriages.
If the 7th Lord is in the Star of Mercury, Younger Spouse is also Possible.
Anyone who seriously cares about astrology would know that it honestly doesn't matter what their child's Sun sign is because there are a million other factors in a birth chart and no two people of the same Sun sign are the same.