It happens to me as well. Since you are using Google services as well as Samsung they merge together on the calenders. When I switched from apple all my calendar stuff synced to Samsung as well.
I had the same issue, I hated seeing the duplicate birthday. This may not be an option for you but because most, if not all my devices are samsung products I just turned off all other calendars including my phone calendar and use my samsung account calendar only. No more duplicates, hope this helps. Cheers
I have the same. Also, would love for them to be able to number the bday so it shows "35th bday" for known bday years and also be able to add a birth date time and place for the contact if known. Also additionally, would be cool to have the ability to add multiple bdays for one contact (like for their kids who don't have a phone yet. Add my niece's bday to my sister's contact info for example.)