Marth---- you need to learn the up throw combo... also try using a shuffle once in a while (short-hopped, fast fall'd, l-canceled, attack), work on edge guarding too... try doing a spike if the fox isnt going for the ledge, and if he is, then either a drop down back air, or a timed forward smash, or d-tilt
Fox---- you seem much more technical than your brother, but you had some problems too... first off, use ur laser...ALL OF THAT TIME YOUR BRO WAS WAVEDASHING BACK AND FORTH WAITING FOR YOU, YOUR LASER COULD HAVE TACKED ON UNREAL DAMAGE... marth's biggest weakness is his lack of projectile, if u stay mid-range with him, he is bound to **** you... by using ur laser, you can get the marth to attack first, which allows to counter attack, (such as wavedashing backwards, then forward smash.... or even a shield grab), but never the less, having him where you want him makes marth easier to beat
overall even match, but more combos are needed, the marth could be a little more technical, and you could use ur range as an advantage