With a few exceptions, the criminal laws of Texas apply equally to a minor as they do to an adult. The difference is in the punishment.
If he touched, even over the clothing, the breast, anus, or vagina of the younger child than this 14 yr old could be charged with indeceny with a child, a second degree felony. This would also be true if he exposed his anus or genitals or caused the other child to expose their anus or genitals.
If he penetrated the vagina with his finger than he could be charged with Aggravated Sexual Assault of a Child, a first degree felony. Note that penetration of the vagina means any penetration, however slight, of the vulva which is the outer covering of the vagina. In other words, unless the girl was clothed any actual touching of the vaginal area would probably count as penetration.
Texas uses progressive sanction levels for juveniles. If this is his first offense and he is adjudicated than he would most likely be placed in level 4 which basically means 6-24 months of probation and in this case, sex therapy. For either of the offenses I mentioned he would have to register as a sex offender for ten years after completing his probation term.
Yes, I would say that this boy needs an attorney.