Hello,
Since all of you are having it, it can be a viral or fungal rash which is contagious or scabies. Scabies is a contagious skin infection caused by a parasite – the mite, which burrows under the host’s skin and causes intense allergic itching. It is transmitted from objects or beddings, but more with direct skin- to – skin contact.
Please get the diagnosis confirmed from a dermatologist and then start with the treatment.
I hope it helps. Take care and regards.