Marius married Caesar's aunt, well before Caesar was even born, making Marius Julius' uncle-in-law. However, at least from my understanding, Marius wasn't very deeply political, and seemed to use his populare stance as a way to advance his military career and obtain power.
Do we know of any instances where Marius and the young Caesar could have potentially met, where Marius may have influenced Caesar? When Sulla was going to execute Caesar but was dissuaded from doing so, he warned that 'in this one Caesar, you will find many a Marius.' Was that just the natural predilection of Caesar, or was he perhaps influenced by his uncle?
No source relates young Caesar and his uncle even meeting but its likely. Caesar's father was tied to Marius, being appointed to supervise the establishment of various veteran colonies that Marius had managed to be granted to his own veteran Roman soldiers. Caesar is known to have had a good relationship with his aunt Julia, Marius' wife, giving her eulogy when she died. He also brought back Marius' statues too. After Sulla took power Caesar fled in fear of being proscribed and killed, and it was only on the part of his mother and other family members begging for his life that Sulls spared him, imparting that in Caesar he saw many Marius. Later in his political life, despite his patrician background, Caesar was a staunch populares, like Marius.
So despite a lack of evidence, he likely had a good relationship with Marius.