London - Michael Phelps has had a busy Olympics and now he's settling into retirement with some quality family time.The 27-year-old US swimming star who won his last-ever Olympic race on Saturday tweeted on Sunday afternoon that he was spending the day with his family."What an amazing day!!!" he wrote, adding that he was with his mom and sisters, Hilary and Whitney."Gotta love the fam!!!" said the 18-time Olympic gold medallist.Phelps later posted a photo of himself with his niece, Taylor, and one of his four gold medals from the London games.