I just looked this one up - as Christopher Guest (5th Baron of Baden) has no heir apparent (no legitimate biological sons) the heir presumptive is his younger brother, the actor Nicholas Guest.
en.m.wikipedia.org/wiki/Baron_Haden-Guest
It’s a pretty new title, as peerages go, created for Christopher’s grandad (a former Labour MP) in 1950
en.m.wikipedia.org/wiki/Leslie_Haden-Guest,_1st_Baron_Haden-Guest
Looks like Nicholas has two daughters so if he does get his big bro’s title he has no heir apparent either, nor does he have an heir presumptive, so most likely the title will become extinct (some variations on this exist but they are written into the original patent from when the peerage was created).
Christopher and Nicholas have an older half brother (the 4th baron’s eldest son) who was born before his parents were married and thus not considered eligible for dad’s title:
en.m.wikipedia.org/wiki/Anthony_Haden-Guest
www.regencyresearcher.com/pages/succession1.html
www.regencyresearcher.com/pages/peer1.html
If Ruby was a bio son there is no reason to believe that a gender transition, even a legal one via a GRC, would’ve made any difference to the male line of succession - see Matilda Simon, 3rd Baron of Wythenshawe - born the male heir apparent of the 2nd baron, who has an older sister.
twitter.com/ripx4nutmeg/status/1527933519682580481
(I suspect being an American is far more of an issue than being trans when it comes to hereditary titles!)