友だちと一緒にごはんを食べているのに、友だちたちはスマートフォンに夢中で、せっかく一緒にいるのに、お互い関心がないようで、さみしく感じます。Even though they are having lunch together, they don't seem to care about themselves. は自然な英語ですか？
I see people sitting with their friends in a restaurant completely absorbed in their phones.
It's a shame they're all together, but they don't pay much attention to each other.
この場合、次のような言い方ができますよ。
ーI see people sitting with their friends in a restaurant completely absorbed in their phones.
「レストランで友達と座っているのに完全に携帯に夢中になっている人を見かける」
to absorb in ... で「…に夢中になる」
ーIt's a shame they're all together, but they don't pay much attention to each other.
「（友達と）一緒にいるのにお互いに関心を示さなくて残念だ」
ご参考まで！
Even though we're together, neither of them seem interested.
Even though they are having lunch together, they don't seem to care about themselves.
一緒にご飯を食べているのに、自分を大切にしていないように見える。
"一緒にいるのに、お互い関心がないように見える"
Even though we're together, neither of them seem interested.
Even though we're hanging out with each other, neither of them seem interested.
Even though we're here together, they both look like they don't care.
カナダ 
アメリカ合衆国 
