RFK Jr. and his wife, actress Cheryl Hines, joined us on Friday's "TMZ Live," and we asked the presidential candidate why he wouldn't be down with a potential Trump pairing.

Cheryl jumped in and told us her husband knows that wouldn't make her very happy ... and he smiled and laughed as he sat back. Smart man.

While there's a marital agreement on the Trump topic, the Kennedy family's been at odds over RFK Jr.'s politics -- most recently, his campaign ad during last week's Super Bowl raised eyebrows.

Kennedy says, like most families, they don't agree about everything ... but it won't be an issue as his campaign moves forward because his Kennedy upbringing taught him to debate things with passion, but also congeniality.

Healthy debate, disagreement, and tough conversations are what RFK Jr. thinks our country needs ... as long as we don't hate on each other.

Speaking of hate, the candidate caught some lighthearted blowback over the viral photos of him walking barefoot on an airplane -- so, naturally, we had to follow up!

RFK says he can't do that anymore after we put him on blast ... even though it sounds like it's his preferred way to fly. Cheryl says he never should've taken off his shoes in the first place.

See, healthy family disagreement!

RFK Jr. and Cheryl seem warmed up for their upcoming comedy show fundraisers ... the first of which kicks off Wednesday night in Los Angeles, with Cheryl serving as host.