Vet said they are young adults, likely up to two years old. Minie is quite petite, hence the name Mini(e), she is still quite shy; Murr is very outgoing and affectionate and purs a lot and this sounds like MURRR....
Not much known about Minie and Murr, they were found together on a street, one injured; they are most likely siblings; they have beautiful and quite unusual white and "salt & pepper" coats.