the leaves look like Syzyygium jambos, which differ from other roseapples in that they are very slender, and will flush a beautiful dark purple.
Very fast growers, I have several in beautiful 30 gallon pots and they look very nice, on the other hand same seeds planted at a friends are over 30 foot tall in <3 years.
Might want to separate now before roots get too tangled if you are planning to keep more than one.