Agree with the scripture above. I pray he doesn't get the tattoo. But your father should show love toward your brother. Both my sons have tattoos, but each time they needed to stay with us, we welcomed them. God says in Jeremiah 31:3; The Lord has appeared of old to me, saying: “Yes, I have loved you with an everlasting love; Therefore with lovingkindness I have drawn you.
When we show God's agape love, we may not agree with what a person does, but we don't make them feel like they are not important and minister to them in the authority of God's Love... Be blessed...
Leviticus 19:28 Ye shall not make any cutting in your flesh for the dead, nor print any marks upon yourselves. I am the LORD.