I don't know how petty this is to point out but *bʰ becoming /f/ in *bʰréh₂tēr to frater is not an example of Grimm's law — *t becoming /ð/ in *bʰréh₂tēr to brother is. Grimm's law is a specific chain shift affecting only the Germanic languages, which Latin decidedly is not an example of.
Well, not just that it's a specifically Germanic thing, but that Grimm's law says that PIE *bʰ corresponds to PGmc *b, just as PIE *b corresponds to PGmc *p, and PIE *p corresponds to PGmc *f.
I don't know how petty this is to point out but *bʰ becoming /f/ in *bʰréh₂tēr to frater is not an example of Grimm's law — *t becoming /ð/ in *bʰréh₂tēr to brother is. Grimm's law is a specific chain shift affecting only the Germanic languages, which Latin decidedly is not an example of.
No, not petty at all! I must have glossed over the Latin part, since I know it's specifically a Germanic thing. Oh, frother!
Well, not just that it's a specifically Germanic thing, but that Grimm's law says that PIE *bʰ corresponds to PGmc *b, just as PIE *b corresponds to PGmc *p, and PIE *p corresponds to PGmc *f.