The England international has been in inspired form for club and country since the start of September, scoring 15 goals in all competitions.
Phil disagrees with his brother, though, claiming that Kane is not yet at the level of another former Tottenham player in Gareth Bale, who himself swapped North London for Madrid five years ago.
"I think Kane has answered every question that has been levelled at him so far and this is just another question he has got to answer," he told Sky Sports News. "Is he now at a higher level that Gareth Bale? I don't think so because Bale has won the Champions League and other titles.
"He's a fantastic striker and he's getting up to world-class level, but Bale is at a world-class level. He's made the move for massive, massive money, he's proved to the world he can do it in European tournaments, Champions League finals.
"He's done it on the biggest stage and it's not just doing it one game, Bale has done it over a period of a time. If you can play for three or four years for a team like Manchester United or Real Madrid then that's when you can talk about being in the greats of European game. Bale has done that."
Kane is expected to start for Tottenham when they take on Madrid in the Champions League on Tuesday evening.