How do you say "a little like..."

Question

If I wanted to say something like "He looks like his brother," I might say 「彼はお兄さんみたいです。」or 「彼はお兄さんのようです。」

But what if I wanted to say that he looks "a little" like his brother? Would I simply add a 少し to the above sentences? (E.g., 彼は少しお兄さんのようです。) Is that grammatical, seeing as there is no verb or adjective for 少し to modify?

Answer 1

If you mention "His face looks like his brother", you should say 彼はお兄さんに似ている(or 彼はお兄さんにそっくりだ). If you want to add "a little", it would be 彼は少し(ちょっと)お兄さんに似ている.

彼はお兄さんみたいです and 彼はお兄さんのようです would be interpreted as "He seems to be (someone's) elder brother" or "His existence(or character) is like a elder brother".

Answer 2

(1) 彼はお兄さんのようです。

If you want to add a meaning of "a little" to the given sentence, it will become as:

(2) 彼は少しお兄さんのようです。

So, your attempt is perfect in the sense of adding a little to (1).
But, for the given sentece, we usually say 彼はお兄さんに似ている or 彼はお兄さんにそっくりだ for "He looks like his brother" as is said in Yuuichi Tam's answer.

And if you want to add a nuance of "a little" to them, you can say 彼はお兄さんに少し似ている but you can't say 彼はお兄さんに少しそっくりだ.

Is that grammatical, seeing as there is no verb or adjective for 少し to modify?

Yes, that is grammatically correct.

この時｛とき｝の「少し」は転成｛てんせい｝名詞｛めいし｝と呼｛よ｝ばれる「名詞｛めいし｝」ですから、修飾｛しゅうしょく｝するものがなくても問題｛もんだい｝なしです。
No verb or adjective is needed to modify for 少し in this case, because it is considered to be a noun, more precisely a "転成｛てんせい｝名詞｛めいし｝ transformed noun".

By the way, transferred noun is what I translated literally, not an established term.

転成名詞とは、他｛た｝の品詞｛ひんし｝の単語｛たんご｝が変化｛へんか｝してできた名詞。
A "Transformed noun" is a noun made by changing a word of other part of speech.

As for 少し, if "少し" is a noun it is literally interpreted like "a small degree".

「少し」は次｛つぎ｝の例｛れい｝のように修飾する対象｛たいしょう｝の有無｛うむ｝により、「副詞｛ふくし｝」と「名詞」の二通｛ふたとお｝りの品詞になります。
"少し" becomes an "adverb" or a "noun" depending on whether there is an object to be qualified like in the following examples. (Source)

• 「この服｛ふく｝は少し大｛おお｝きい」⇒副詞 adverb
• 「車｛くるま｝を少し動｛うご｝かす」⇒副詞 adverb
• 「少しの間{あいだ}待｛ま｝っていてください」⇒名詞（転成名詞） noun
• 「少しはできるようだな」⇒名詞（転成名詞） noun