Japanese people aren't really familiar with hosting birthday parties for one another.
It's not really a Japanese custom to invite friends over to your house to celebrate someone's birthday.
ーJapanese people aren't really familiar with hosting birthday parties for one another.
「日本人は互いに誕生日パーティーを開くのにあまり馴染みがない」
to be familiar with ... で「…に馴染みがある」
to host birthday parties で「誕生日パーティーを開く・開催する」
ーIt's not really a Japanese custom to invite friends over to your house to celebrate someone's birthday.
「誰かの誕生日を祝うために友達を家に招くことは日本の習慣ではない」
to invite friends over to one's house で「家に友達を招く」
to celebrate one's birthday で「人の誕生日を祝う」
ご参考まで！
カナダ 
