Can co-parents-in-law marry? For example, a husband's father and a wife's mother (but applied to Islam)

Same question as here but for Islam. I don't see how a married couple's becoming step-siblings is any different from step-siblings' become a married couple. Suppose Alice and Bob are widows (or single adoptive parents or unmarried biological parents or whatever) and their respective children are Charlie and Dalia. Supposed all 4 are not married (or were never married or whatever, depends if widow or not). If Alice and Bob marry, then Charlie and Dalia cannot marry. But if Charlie and Dalia marry, then can Alice and Bob marry afterwards?