------
## 最终结论
```python
def group_tuples(tuples_list):
    grouped_dict = {}
    
    for a, b in tuples_list:
        if a in grouped_dict:
            grouped_dict[a].append(b)
        else:
            grouped_dict[a] = [b]
    
    result = []
    for key, values in grouped_dict.items():
        result.append((key,) + tuple(values))
    
    return result

# Test cases
assert group_tuples([('x', 'y'), ('x', 'z'), ('w', 't')]) == [('x', 'y', 'z'), ('w', 't')]
assert group_tuples([('a', 'b'), ('a', 'c'), ('d', 'e')]) == [('a', 'b', 'c'), ('d', 'e')]
assert group_tuples([('f', 'g'), ('f', 'g'), ('h', 'i')]) == [('f', 'g', 'g'), ('h', 'i')]
```