Thanks Lynn, this is the plan- add 3-rd node to cluster, install 2016/2014 version on all 3 nodes (first 2 nodes certainly have already 2016 running) and make 3-nd node default for 2014 instance.
Any pitfalls we should be aware of, any supporting docs from MS? Really appreciate your comments.
On second thought- seems 3 nodes cluster won't work for us as installing new instance on extra node will certainly require extra license for sql server 2014. Therefore to rephrase my question-
can we add sql server 2014 instance to 2 nodes cluster with 2 sql server 2016 instances already running there? Thanks
If you are adding a SQL Server 2014 instance to both nodes and they are supporting each other than yes.