In the Anime and Manga
Little is known about the relationship involving Rome and Germania other than the fact that Germania had served the role as Rome's bodyguard, and was also the same person that had taken his life. It is shown in the anime and manga that Germania is constantly annoyed by the fact that all Rome talks about is usually wine, women, and fighting. Once, when Rome felt depressed because he lost a fight, Germania tried to cheer him up, telling that Rome could win the next time. Rome immediately becomes, much to Germania's annoyance, happy. Due to the fact that there isn't much more told about their relationship, let alone the characters themselves, this couple is more of a minor pairing at the time being, but the fan base is slowly growing.
Rome and Germania are in fanworks often as fathers/grandfathers depicted. Rome's children are Italy and Romano, sometimes he is shown with Spain and France. Germania is seen with HRE, Prussia, Austria and Swiss. Sometimes they're living in a big household together.
Some fans also believe that Austria might be a lovechild of Rome and Germania as he definitely is a Germanic but has several traits (both physical and personality-wise) that are typical for the Italian family.
- Grandpa Rome and Germania (Hetalia: Axis Powers Volume 2)