How to join two objects to share values but maintain the original name? Aka N-body merger

As the title says, I am working on an N-body simulation I found on YouTube. The current script has gravity turned off when radius is small enough. However, I’d like to join the two objects (body and otherbody) into a new one which behaves according to the same rules, it just has the properties of both added. How do I do this? Here is the code in question.

import pygame
from sys import exit
import math as m
import itertools
import random

pygame.init()
WINDOW_SIZE = (1500,1500)
WINDOW = pygame.display.set_mode(WINDOW_SIZE)
CLOCK = pygame.time.Clock()
G=1

BACKGROUND = pygame.Surface(WINDOW_SIZE)
BACKGROUND.fill("Black")
BACKGROUND_RECT = BACKGROUND.get_rect(center=(500,500))

class Body(pygame.sprite.Sprite):
    def __init__(self, mass, radius, init_position, color, vx, vy):
        super().__init__()
        
        self.image = pygame.Surface([(radius*2),(radius*2)])
        self.image.fill("Black")
        self.rect = self.image.get_rect(center=init_position)
        pygame.draw.circle(self.image, color, (radius,radius), radius, 0)
        
        self.mass = mass
        self.radius = radius
        self.x_pos = init_position[0]
        self.y_pos = init_position[1]
        
        self.vx = vx
        self.ax = 0
        self.vy = vy
        self.ay = 0
    
    def set_vy(self,value):
        self.vy = value
    def set_xv(self,value):
        self.vx = value
    def set_ay(self,value):
        self.ay = value
    def set_ax(self,value):
        self.ax=value
        
    def change_x_pos(self,value):
        self.x_pos+=value
    def change_y_pos(self,value):
        self.y_pos+=value
    def change_vx(self,value):
        self.vx+=value
    def change_vy(self,value):
        self.vy+=value
        
    def update_pos(self):
        self.rect.center = (round(self.x_pos), round(self.y_pos))
        
    def animate(self):
        self.change_vx(self.ax)
        self.change_vy(self.ay)
        
        self.change_x_pos(self.vx)
        self.change_y_pos(self.vy)
        
        self.update_pos()

    def gravity(self, otherbody):
        dx = self.x_pos - otherbody.x_pos
        dy = self.y_pos - otherbody.y_pos
        
        if dx < self.radius*2 and dy < self.radius*2:
            pass

        else:
            try:
                r = m.sqrt(dx**2 + dy**2)
                a = G*otherbody.mass/r**2
                theta = m.asin(dy/r)
        
                if self.y_pos > otherbody.y_pos:
                    self.set_ay(-m.sin(theta)*a)
                else:
                    self.set_ay(m.sin(theta)*a)
                
                if self.x_pos > otherbody.x_pos:
                    self.set_ax(-m.cos(theta)*a)
                else:
                    self.set_ax(m.cos(theta)*a)
            except ZeroDivisionError:
                pass


body_group = pygame.sprite.Group()
BODYCOUNT=3
for i in range(BODYCOUNT):
    body_group.add(Body(10, 3, (random.randrange(100,900), random.randrange(100,900)), "White", 0,0))
    
body_list = list(body_group)
body_pairs = list(itertools.combinations(body_list,2))

while True:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            exit()
    WINDOW.blit(BACKGROUND, BACKGROUND_RECT)
    
    body_group.draw(WINDOW)
    
    for body, otherbody in body_pairs:
        body.gravity(otherbody)
        otherbody.gravity(body)
        body.animate()
        otherbody.animate()
    
    pygame.display.update()
    CLOCK.tick(60)

The part in question is if dx < self.radius*2 and dy < self.radius*2: pass

How do I join the objects body and otherbody into a new body?

Also the current version of the script only has one object being attracted to the other, not equal attraction. If you see why, can you point it out?