Parenthood does address infidelity in a couple arcs over the show, but overall the show goes out of its way to show partnerships of all stages through a ton of ups and downs working through trust and communication to support each other. It's a remarkably wholesome show, sometimes engineered to make you cry, that is as much about relationships as being parents. Highly rec'd.
Also for something lighter, echoing the Modern Family rec from above. You can feel its run living through how we talk about love and diversity morphing through time, with some regrettable jokes (mostly from Jay about Gloria's ethnicity and Mitch's identity, and Mitch/Cam about Lilly's ethnicity, but like The Office I think that's part of the point?) but never comes close to touching infidelity aside from Phil's 100% innocent crush on Gloria.