It is not possible to reliably tell male from female by their size. I find, here, usually, that the females are happy to share a bowl with another female (although not always) or sometimes a male. The males will not normally share a bowl with another male unless it is a youngster. The females will also share with a youngster. So my guess would be that it is not a male and female. A slightly more reliable way to tell, is if you see males and females interacting. The male will often begin to circle the female during courtship. She will turn round, huffing as she goes, and keeping her head towards him.
Nice to hear that you have had 4 hogs visiting. I hope you continue to enjoy watching their activities.