What is the nexus between the two? People across this planet, from a variety of cultures marry for a variety of reasons. How do you isolate ?chemistry? or define its presence or quantify consequences? It seems you are chasing an undefined enigma.
My question is this: Do you think two people that have children while really living together for material reasons rather than "chemistry" has any bearing on the health and genetics of their children?
Do you think these children can be more likely to be born with health problems than children of those people that truly love each other?
Using nature as your standard, there are very few animals that mate for life. Among those that do, do you attribute it to love or just instinct? How do these and those animals that do not mate for life fit into your model?
My simple answer is: no.
[Long term] physical health [trends] has probably more to do with the adjustment to the vagaries of the human condition.