The RPL9P15 gene is a member of the ribosomal protein gene family. It encodes a pseudogene related to the RPL9 gene that codes for a component of the ribosome, which is crucial for protein synthesis. Pseudogenes are non-functional segments of DNA that closely resemble functional genes, but they are not translated into proteins and don't have a known functional purpose under normal physiological conditions.

### 1. Related Genes
While the summaries provided by NCBI and UniProt may not list specific associated genes, typically, related ribosomal protein pseudogenes and their functional counterparts may include:

- **RPL9**: The functional homolog of RPL9P15, encodes a ribosomal protein that is a part of the 60S ribosomal subunit.
- Other ribosomal protein genes in proximity, which may share regulatory mechanisms or epigenetic modifications, include RPL7, RPL8, RPL10, etc.

It's worth checking databases like Ensembl or KEGG for more comprehensive lists of associated genes through co-expression or pathways.

### 2. Aging and Age-related Diseases
While specific associations of RPL9P15 with aging or age-related diseases are not well-characterized, ribosomal proteins and the ribosome's functionality are generally implicated in:

- **Cellular senescence**: Aberrant ribosome function is known to contribute to the aging process.
- **Age-related pathologies**: Dysregulation in ribosomal protein genes has been observed in various cancers and may be linked to age-associated diseases, although no direct studies for RPL9P15 have been elucidated.

Further research in the context of age-related mechanisms of cellular stress and the role of pseudogenes in gene regulation may provide insights.

### 3. Drug Interactions
Due to the nature of RPL9P15 being a pseudogene, there are no known direct drug interactions associated with it. However, the functional counterpart RPL9 can interact with various agents that influence ribosomal biogenesis. Common drug classes may include:

- **Antibiotics**: Such as those affecting ribosomal function, may indirectly affect pathways involving ribosomal protein genes.
- **Chemotherapeutics**: Certain cancer treatments can target ribosomal assembly or function, impacting the overall regulatory environment involving ribosomal proteins.

For more specific interactions, literature searches should be conducted for drugs targeting RPL9 if relevant in the context of therapeutic studies.

### 4. Pathways and Biological Processes
Since RPL9P15 is a pseudogene, it is not typically involved in any defined pathways. However, associated biological processes relative to its functional counterpart, which might conceptually implicate RPL9P15 in broader context, include:

- **Ribosome biogenesis**: The synthesis and processing of ribosomal RNA and assembly of ribosomal proteins.
- **Translation**: In the context of ribosomal function, whereby the ribosome translates mRNA into proteins.
- **Cellular metabolism and growth**: Since ribosomal proteins are fundamental to protein production, they play crucial roles in cellular metabolism and growth regulation.

Due to the inherent limitations of studying pseudogenes, their implications in the above pathways are less direct and more of an indirect association through their expressed counterparts.

### Conclusion
The RPL9P15 gene, as a pseudogene, holds potential insights into evolutionary genetics and expression regulation in relation to its functional counterparts and broader biological themes like aging or disease. For a thorough understanding, more focused experimental or computational studies would be required to elucidate its precise role and associations.