Liverpool were hosting Union Saint-Gilloise in the Europa League with the Reds coming away with a 2-0 win thanks to goals from Ryan Gravenberch and Diogo Jota.
However it was the two siblings on opposing sides who stole the headlines.
Fresh from winning the World Cup with Argentina last year, Alexis is adapting to life at Anfield following his move that could be worth up to £55million.
Kevin, who is one year older, joined the Belgian side from Argentinos Juniors over the summer with the chance to face the Premier League star in Europe's second competition, something that the brothers say was a big occasion for all of the family.
"It was really nice for the family, very emotional," Alexis told TNT Sports.
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"I've played against my older brother before but never against Kevin - it was special.
"My dad was here too, he knows what it means, he cried a little bit."
Kevin added: "He was the reason I suffer today, but it was a very special moment.
"Of course, Liverpool, maybe in the last match, come to Belgium and we can get revenge maybe.
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Asked whether they will swap shirts after the game, Alexis joked: "I don't know if he wants a shirt from another player!"