Three some

My husband and i have been together for 13 years and our sex life is fantastic but we started talking about having a 3some a few years back with either another guy or girl. We did end up having one wirh another guy and it was awesome but now I am thinking about having one with another girl. No one I know has ever had one but I did a little research and found alot of people mentioned a threesome with a girl ended the relationship or marriage. since our marriage is stronger than ever after having one with another guy wondering if it will be the same with a girl. just want to see what people who have had one think, thank you!