The trio sat together in the stands at the stadium in Twickenham, London, and when the Welsh national anthem began, Kate, 33, and William, who is vice patron of the Welsh Rugby Union began singing — in Welsh.
Harry, 31, who still has the rugged ginger beard he grew during a recent trip to Africa, watched the pair but didn't join in, as he is the honorary president of England Rugby.
It was a nail-biting match, which saw Wales score a stunning 28 to 25 victory over England. Afterwards, William, 33, jokingly commiserated with his younger brother and put his arms around his wife, cuddling her and sweetly laying his cheek next to hers. The Duchess of Cambridge's new bangs could also be seen in the pic.
Wales holds a special place in the royal couple's heart as they shared a cozy farmhouse on the Welsh island of Anglesey before their marriage and for a couple of years following their April 2011 wedding.
They moved back to London and into a newly renovated apartment at Kensington Palace after George was born and William ended his tour of duty as a search and rescue helicopter pilot.