Some guineas can give the appearance of being permanent mates. Most male guineas will mate with any available females even though they may show a preference for one particular hen. Ideally there should be a slightly higher number of hens than cocks in a flock.
I would not recommend getting one male and a few females. I recommend a minimum of 10 guineas for a flock. They are a flock bird and do better in larger groups. The only way to get sexed guineas is by getting adult guineas. If you only have one male and something happens to it, that will leave you without any breeders. Unfortunately there are very many things that can happen to guineas.