Messi claimed another LaLiga title this season but Champions League and Copa del Rey defeat to Liverpool and Valencia respectively has seen the five-time Ballon d'Or winner ruthlessly trolled by his own son.
"Thiago never misses a match," Lionel Messi told TyC Sports. "Mateo loves football, he wears all the shirts.
"We were playing at home and he said to me, 'I'm Liverpool, who beat you'; 'Valencia won, eh - I'm Valencia'.
"The TV is there, and he cheers Madrid's goals to annoy his brother. He's the one who is a Madrid fan."
Messi's comments caught the attention of former Madrid full-back Arbeloa, who won LaLiga and two Champions League trophies during his time at the Santiago Bernabeu.
"Let's get him [Mateo] signed," ex-Spain international and World Cup winner Arbeloa tweeted.
Messi – preparing for the Copa America with Argentina – scored a LaLiga-high 36 goals in 2018-2019 as he claimed his sixth European Golden Shoe.
The 31 year-old finished the season with 51 goals in all competitions as Barca reached the Champions League semi-final and Copa del Rey decider.