If God allows people to understand that Jesus was His Son and that’s the only way they can come to this conclusion, then is that free will? Also, why would He not allow someone to believe in Jesus?

God is indeed sovereign, or He rules, over everyone’s salvation. As Christ Himself said, No one can come to me unless the Father who sent me draws him, and I will raise him up at the last day—Jesus Christ, John 6:44. Yet at the same time, people are morally free agents who are responsible for the choices and actions they make. That tension between God’s sovereign will and human free will is displayed throughout the Scriptures. Adam and Eve, for example, were free to choose or free to avoid the forbidden fruit in the Garden of Eden. To choose to eat of the forbidden fruit demonstrated their freedom to choose to sin and rebel against God and His specific command. To avoid the forbidden fruit represented an equally free choice to continue in obedience to His word. Obviously, and unfortunately, they chose to sin. When Christ Himself arrived in this world, as the apostle John writes, He came to that which was his own, but his own did not receive him. Yet to all who received him, to those who believed in his name, he gave the right to become children of God—John 1:11-12, those verses showing both responses to the Savior. Now God is the author of salvation in every respect, and we of course receive the benefits of that salvation, but God’s authorship is no way overrides our will; God is not manipulating us. His unconditional love planned salvation, but that unconditional love is never forced on those unwilling to receive it. It is also true that God knows the end from the beginning; that is part of His omniscience (His all-knowingness). As He said through the prophet Isaiah, I make known the end from the beginning, from ancient times, what is still to come—God speaking, Isaiah 46:10a. Just because God knows that completely doesn’t mean humans don’t have free will. Our free actions do not take place because God knows them in advance; rather, God knows them in advance because He knows they will take place. In other words, although God absolutely knows the future, He has predetermined that that future takes place in the context of human freedom. Therefore, our choices are made, as Peter wrote, according to the foreknowledge of God the Father—I Peter 1:2a. The overriding fact is that God has declared His passion for our salvation. As Paul wrote to Timothy, [God our Savior] wants all men to be saved and to come to a knowledge of the truth—Paul, I Timothy 2:4, which aligns completely with some of Peter’s final words: The Lord . . . is patient with you, not wanting anyone to perish, but everyone to come to repentance—II Peter 3:9b. This is God’s desired or preferred will for all mankind, despite the reality that not everyone will choose His salvation. God’s sovereign or determined will of course determines the outcome of those who choose rebellion against Him. Despite the potential for confusion, what we need to remember is God’s very transparent, very declared passion for everyone’s salvation. As Peter said so well, bringing in Old Testament verses in the process, “HE HIMSELF BORE OUR SINS” in his body on the tree, so that we might die to sins and live for righteousness; “BY HIS WOUNDS YOU HAVE BEEN HEALED.” For “YOU WERE LIKE SHEEP GOING ASTRAY,” but now you have returned to the Shepherd and Overseer of your souls—I Peter 2:24-25 (quoting Isaiah 53:5-6.
If none of this (or anything else) seems to make any particular sense, it is always good to remember that God as an infinite being will always be at some level completely mysterious to us very finite human beings. One of the drawbacks to systematic theology is that it tries to explain God. God cannot be put in one of our human boxes. While there are certainly things about Him we can know—largely due to His word—there are many things that will always remain unknown to us. As God Himself said through the prophet Isaiah, For my thoughts are not your thoughts, neither are your ways my ways,” declares the Lord. “As the heavens are higher than the earth, so are my ways higher than your ways and my thoughts than your thoughts—Isaiah 55:8-9. Maybe that is partially why Paul told the church at Corinth, We live by faith, not by sight—Paul, II Corinthians 5:7 for, as the writer of Hebrews understood, [W]ithout faith it is impossible to please God—Hebrews 11:6a.