If we are going to talk about 35 years of illumos linkage, we as well go all the way. Using you notation: Solaris <—- SVR4 [0] <—- AT&T System III [1] <—- Bell Labs Version 7 Unix [2] <—- the birth of Unix at Bell Labs in 1969 [3].

Besides the direct lineage, it’s interesting to see cross pollination between different operating systems over the years. Like BSD’s socket interface spreading everywhere (including Windows), ZFS from OpenSolaris to FreeBSD & Linux, then bhyve from FreeBSD to illumos.

[0]: https://en.m.wikipedia.org/wiki/UNIX_System_V#SVR4

[1]: https://en.m.wikipedia.org/wiki/UNIX_System_III

[2]: https://en.m.wikipedia.org/wiki/Version_7_Unix

[3]: https://en.m.wikipedia.org/wiki/Unix

You missed the branch there for Solaris 1.x (aka SunOS) which was a BSD derivative.

One of the nifty things about Solaris was all the compatibility code they had. You could set environment variables and compile against BSD, SysV, and a variety of other "standards" - they tried to make it so that anything that could compile on a UNIX would compile on Solaris.