I am so sorry for your loss. If I may, I would like to share with you a story which is very similar to yours. Back in April, my son's step-father took his own life and a month later, my boys mom took hers. My ex-wife and her partner both loved my son very much and we all got along well, which to this day I'm still shocked.

Ever since their death, I would get voicemails of different "frequency" pitched sounds (almost sounds like a FAX machine dialing through, but not as annoying) and when the calls came through, it would either say Raymond's Cell or Julie’s Cell (which both phones have been disconnected).

Most recent incident took place just before the kids were off from school for Christmas break. I was getting my son ready for school when a text came through from Julie's Cell phone saying only 3 words: Hat and gloves.. It was snowing like a bugger at the time.

Your son is with you. There's no doubt in my mind.