These six brethren - Probably pointing to them, being present, as proper persons to confirm the truth of what he was delivering.

And the Spirit bade me go with them, nothing doubting,.... See Gill on Acts 10:20,
moreover, these six brethren accompanied me; it seems by this, that the six brethren that went along with Peter from Joppa to Caesarea, came also with him from thence to Jerusalem, and were now present, whom he points to; so that it looks as if Peter was aware, that he should be called to an account for his conduct, when he should come to Jerusalem; and therefore brought these six brethren with him, to be witnesses for him, of what they had seen and heard, which was a very wise and prudential step:
and we entered into the man's house; the house of Cornelius, for entering into whose house they were contending with him, and where he entered not alone, but the six brethren with him; the Ethiopic version wrongly reads "three".

we entered the man's house--No mention of Cornelius' name, much less of his high position, as if that affected the question. To the charge, "Thou wentest in to men uncircumcised," he simply speaks of the uncircumcised "man" to whom he had been divinely sent.