Brendan & May

Your rivals in Pokemon Ruby and Sapphire take on a different approach. For the first time ever your primary rival is the character opposite to your gender: May if you're a boy and Brendan if you're a girl. They are the child of Professor Birch and aid him in his research. They also appear more friendly than rivals of past games. As well, unlike previous games they don't make it as far with their teams as you and you don't get to see the final evolution of their starting Pokemon. The first time you meet the rival is after you move in, as asked by your mother..

Encounter #1: Route 103

Details:
Shortly after you receive your first Pokemon, the professor asks you to summon their child from Route 103. This is the second time meeting them and now they have a Pokemon to battle you with. As with previous games the Pokemon always has a type advantage to yours

Pokémon Trainer Brendan/May Treecko
Battle Type
Single Battle
Level 5
Mudkip Chosen

Pokémon Trainer Brendan/May Torchic
Battle Type
Single Battle
Level 5
Treecko Chosen

Pokémon Trainer Brendan/May Mudkip
Battle Type
Single Battle
Level 5
Torchic Chosen
Encounter #2: Route 110

Details:
A bit later on you will meet your rival again under the Cycling Road. Their team now has a Pokemon from all three of the starting Pokemon types making it more rounded. You will receive the Itemfinder for defeating them

Pokémon Trainer Brendan/May WailmerNumelGrovyle
Battle Type
Single Battle
Level 18Level 18Level 20
Mudkip Chosen

Pokémon Trainer Brendan/May WailmerShroomishCombusken
Battle Type
Single Battle
Level 18Level 18Level 20
Treecko Chosen

Pokémon Trainer Brendan/May ShroomishNumelMarshtomp
Battle Type
Single Battle
Level 18Level 18Level 20
Torchic Chosen
Encounter #3: Route 119

Details:
Your third encounter is on Route 119 near the Weather Institute. It is very similar to the last one but now the levels are a bit higher. After defeating your rival you will receive HM02, which will allow you to teach your Pokemon Fly.

Pokémon Trainer Brendan/May NumelWailmerGrovyle
Battle Type
Single Battle
Level 29Level 29Level 31
Mudkip Chosen

Pokémon Trainer Brendan/May WailmerShroomishCombusken
Battle Type
Single Battle
Level 29Level 29Level 31
Treecko Chosen

Pokémon Trainer Brendan/May ShroomishNumelMarshtomp
Battle Type
Single Battle
Level 29Level 29Level 31
Torchic Chosen
Encounter #4: Lilycove

Details:
The final battle is outside the Lilycove Department Store, and you have to best your rival once more to get inside. This time they add a Swellow to their arsenal. Unfortunately, they don't fully evolve their starter Pokémon in this game, which prevents you from being able to see them in your Pokédex

Pokémon Trainer Brendan/May SwellowNumelWailmerGrovyle
Battle Type
Single Battle
Level 31Level 32Level 32Level 34
Mudkip Chosen

Pokémon Trainer Brendan/May SwellowWailmerShroomishCombusken
Battle Type
Single Battle
Level 31Level 32Level 32Level 34
Treecko Chosen

Pokémon Trainer Brendan/May SwellowShroomishNumelMarshtomp
Battle Type
Single Battle
Level 31Level 32Level 32Level 34
Torchic Chosen