My heart goes out to you and family in this time of difficulty.

Law does speak to your question, and the only proper means for you to gain some closure is to consult with a licensed attorney near you. They can give opinion shaped by law on your facts re handling of your dear sons' cremains.

We who here have lent supportive thoughts cannot give the legal advice which may help you. This being said, the loving thoughts shared relative to holding memorial service(s) is wonderfully stated apart from burial.

A memorial helps to bring thoughts, feelings, and deeply held hopes for the best for your loved ones shared by you and many others to a place where, shared in grief and joy and loving reflection, aid each of we who mourn to move forward in life. This is even many times done without a body or remains at all.

I pray you, your family/friends, and your ex will find peaceful resolution to your double tragedy.

Peace,
M56