Genetic relationships between languages (as established through comparative linguistics) can lead to similarities that can lead to certain advantages when learning languages from the same family (e.g. multiple Germanic languages, multiple Slavic languages, etc.)
However, languages can also have similarities without being historically related. Linguistic typology is the field of linguistics that "studies and classifies languages according to their structural and functional features" (Wikipedia).
One important language feature concerns the basic order of subject, verb, and direct object in sentences, e.g. subject–verb–object (SVO) languages (English, Chinese, French, ...), verb–subject–object (VSO) languages (Arabic, Irish, Tagalog, ...), etc.
Learning a (genetically unrelated) language with many typological similarities to one you know is presumably easier than learning a (genetically unrelated) language with fewer typological similarities. Even though this sounds plausible, I would like to know if any studies have been done on how these typological similarities facilitate language learning.