Son predicting baby

So my 4 yr old grew out of a pair of shoes and as I was deciding whether to hold on to them or put them in the clothing drive he told me that his little brother will wear them when he gets bigger. He doesn’t have a little brother and it completely freaked me out. We’ve been trying for another baby for a while now with no luck. I usually don’t believe in signs like this but maybe he knows something I don’t?? I’m in my TWW. Has this happened to anyone before??