Were Mickey and Minnie Mouse twins? No, that's not true: According to Walt Disney, Mickey and Minnie Mouse were married off screen, although when their roles required, they were sometimes presented as a courting couple. Minnie has been the leading lady alongside Mickey Mouse ever since their 1928 screen debut in the famous animated short film "Steamboat Willie"
The story originated in a post (archived here) on Facebook where it was published on July 31, 2020. It opened:
all these years i thought mickey mouse & Minnie dated 😭.
whole time they twins 😭
This is what the post looked like on Facebook at the time of writing:
(Source: Facebook screenshot taken on Mon Nov 16 00:50:50 2020 UTC)
In a Valentine's Day blog post in 2013, "Mickey's First Love: Minnie," for what would have been their 85th anniversary, waltdisney.org reviewed some of the appearances of Mickey and Minnie together. Included is the answer to the question about their relationship:
In the September 30, 1933 issue of Film Pictorial magazine, Walt Disney addressed that very subject. "In private life, Mickey is married to Minnie. A lot of people have written to him asking this question, because sometimes he appears to be married to her in his films and other times still courting her. What it really amounts to is that Minnie is, for screen purposes, his leading lady. If the story calls for a romantic courtship, then Minnie is the girl; but when the story requires a married couple, then they appear as man and wife. In the studio we have decided that they are married already."
Released on November 18, 1928, Steamboat Willie, and Mickey & Minnie Mouse will be 92 years old this year.