Neymar, 25, was heavily linked with the Champions League winners during the early days of his career at Santos before deciding instead to move to the Nou Camp during the summer of 2013.
The Brazil international has since developed into a crucial player for Barcelona, forming an impressive attack alongside Lionel Messi and Luis Suarez.
Neymar signed a new deal at Barcelona last summer after being again linked with Real Madrid, Manchester United and Paris Saint Germain.
However, his future at Ernesto Valverde's side has been thrown into question in recent days after it emerged that the Ligue 1 giants are considering meeting his €222m (£198m, $258m) release clause to lure him away from Barcelona.
The La Liga side have insisted that Neymar is not for sale at any price after the Brazil international enjoyed another impressive 2016-2017 campaign, scoring 20 goals and providing 27 assists in 45 appearances.
Gerard Pique appeared to end the speculation on Sunday after posting a picture of himself with Neymar on his social media channels with the caption: "He stays".
However, reports in Spain are suggesting that the saga is not over yet with Neymar still considering leaving Barcelona in order to become the leader of PSG.
Casemiro has now added more uncertainty to the saga after backing his national teammate to join him at Real Madrid.
"It's up to Neymar to make a decision on his future. He knows what he has to do. Why not play at Real Madrid? He would be welcome here," the Real Madrid midfielder said to GloboEsporte.com following Los Blancos' defeat to Manchester United in the International Champions Cup on Sunday.
"I haven't spoken with Neymar recently. He is a great player. I have great admiration for him. He knows what he does, he's well advised, his father is a great person and he knows what he's doing. If he leaves Barcelona, I wish him all the luck in the world, if he stays, I also wish him all the luck in the world. Neymar is very important for the national team because we always count on his great football."