Going from Guarani to Welsh (Cymraeg) has a composite linguistic distance of 78% (heuristic estimate). Below is the dimension-by-dimension breakdown.
Shared vocabulary, cognates, and loanwords.
Morphology, syntax, word order, cases.
Shared sounds and phoneme inventory.
Latin → Latin
Tupian ↔ Indo-European
The 5 languages with the lowest linguistic distance from Guarani:
A quick 3-question check between Guarani and Welsh. No signup.