In the members of family Fabaceae, the petals show descending imbricate aestivation.

Answer

### Step-by-Step Solution:

1. **Understanding Estivation**:
- Estivation refers to the arrangement of petals or sepals in a flower before it opens. It is crucial to understand this concept as it helps in identifying the floral structure of different plant families.

2. **Identifying the Family**:
- The question specifies the family Fabaceae, which is commonly known as the legume family. This family includes a variety of plants such as peas, beans, and lentils.

3. **Describing the Type of Estivation**:
- In the Fabaceae family, the petals exhibit a specific pattern of arrangement known as "descending imbricate estivation." This means that the petals are arranged in such a way that they overlap each other, with the largest petal positioned at the back.

4. **Analyzing the Arrangement**:
- In descending imbricate estivation:
- The largest petal is referred to as the **standard petal** (posterior).
- There are two smaller petals on the sides known as **wings**.
- Additionally, there are two other petals that are fused together at the base, referred to as the **keel**.

5. **Visualizing the Structure**:
- To visualize this arrangement:
- Imagine the standard petal at the back, then the two wing petals overlapping it from the sides, and finally, the keel petals at the front, which are often fused together.

6. **Conclusion**:
- Therefore, the statement that in the members of the family Fabaceae, the petals show descending imbricate estivation is true. This specific arrangement is characteristic of the flowers in this family.