When two people have different experiences, assumptions, and family life, they likely have to work harder to understand each other. Since you asked about studies, here’s a literature review of 50 years of research on interracial marriages: bit.ly/50-years-loving (BC access only). For a more narrative perspective, try the recent film Loving (Law Library feature film collection), about the couple in the landmark Supreme Court case. The advantage of ethnic and SES differences is that you can’t help but recognize & address them; many couples have differences they never acknowledge until it’s too late. In that sense, differences are universal, and you just need to focus on honesty, trust, and compassion.