The onion (Allium cepa) is a close relative of garlic (A sativum) so it is hardly surprising that they share many characteristics, not least their purported health benefits, of which there are several.
Both are held to be good at preventing platelet agglutination, an important consideration in recovering stroke victims. Both are recommended as a natural antiviral in traditional cold remedies. Both are claimed to be mild antihypertensives. Both are said to be useful in various respiratory diseases.
Both are even supposed to reduce varicose veins. So if your partner is OK with onion breath rather than garlic breath, you can still eat healthily.