Swollen Foot

Since I was a child (about 10 yrs) my right foot seems to swell up in the summer. No pain. As a 10 year old, a doctor put my foot in a cast, which didn't work - they didn't know what to do. I'm 55 years old now and have dealt with this all my life - I only get swelling on that one foot in a few different ways - summer heat; airplane rides or if I've had too much alcohol. Gout has been ruled out. I know that my grandmother also had swollen feet (both) and my 88 year old mother has them as well - so bad that her shoes are tight - her doctors cannot figure it out either. It really doesn't bother me - but I really don't want to have my feet turn out like theirs are. I'm an active person and I take no medications. Any clue what this might be?