Awww. This is so sweet. There is nothing to get worry about it, they are just kids.
My son was in love for the first time at age 4 in Pre-K. He came home one day and told me, mom I like 2 girls, can I have 2 girlfriends? I say not, you must choose one. But of course I worry a little bit, I thought about myself, then and ask my husband if he felt in love when he was 4, the answer was not... At that time my son and I were having therapy for his behavior for ADHD I had the chance to ask the professional, he told me it was normal. Later on my son pick up his girlfriend, she was a Japones girl, that girl knock my son's heart. You have not idea how in love my son was, he wrote and draw pictures of her and him together holding hands, or he giving flowers to her, all that pictures was over and over everyday in the walls, in his homework, in the books at home, in the patio and he will tell everybody how in love he is . He plan to marry her, after he finish school of course, he said they are going to have 2 kids, he put names to the kids, he also told me, he will be a surgeon, he will buy a big house for her and their kids. We were military and we used to move every 2 years, so after we moved, he was sad, he wrote a lot of letter to her, he wonder if she miss him, if she is thinking about him, if she is sad because he is in another country, he was a sad boy. I try to comfort him, and tell him that yes, she is missing him a lot, but the same way we move, she may move soon also, but communication is important. The real thing is that that girl didn't know my son was so in love with her, and time means healing for all of us. Later on in kinder he got another girlfriend, then in first grade. In second grade he and his best friend got girlfriends also, but again, the girl didn't know they had boyfriends hahaha. Now he is in 3 grade, and he didn't mention about a girl jet. I ask him, he say not, and smile. All kids are, and feel different, my second child is 5 and he didn't have a girlfriend yet. Wish you the best luck for you family, just enjoy your son's feeling, and let him know how in love you are with his mom.